Ink-jet cartridges used in printers with ink jet systems typically have an ink holder inside an ink storing container for holding the ink. Reticulated polyurethane foam has been used for years in ink-jet cartridges for ink holders to control the back pressure and/or regulate the ink flow to the print nozzles. It is well known in the art that controlling the foam pore size and compression ratio of the foam allows the back pressure (i.e. capillarity) to be tailored to the specific application for which the foam is being used. Typical reticulated urethane foam has a void volume of 97% which enables it to fill an entire ink cartridge while occupying only 3% of the volume. However, despite the advantages of using reticulated polyurethane foam in ink jet applications, there are some drawbacks.
First, the correct stiffness for the foam is hard to obtain. Ink jet cartridges are assembled on automated lines where the foam part comprising the ink holder has to be very quickly and mechanically stuffed or inserted into the ink cartridge. Some ink cartridge designs are not uniformly shaped and can have tapered walls. If the foam does not have the correct stiffness or integral strength it will deform and any deformation in the foam part can cause failure in its ability to perform. In addition, if the foam is too stiff, it will be more difficult, and require more force, to insert.
Second, the foam needs to wet-out rapidly and polyether urethane foams are inherently hydrophobic. Once the ink cartridge has been fitted with the foam part that comprises the ink holder, it moves to an automated ink fill station where the ink is injected into the foam ink holder contained within the ink cartridge. The ink is injected into the foam ink holder at a very high rate; it is typically injected in a matter of seconds. Despite the hydrophobic nature of the foam, it needs to wet-out rapidly to allow for rapid and complete uptake of the ink in order to completely fill the ink holder with ink.
These drawbacks or problems are experienced with standard polyether urethane foams that are used in ink jet applications as well as other applications. Accordingly, there is a need for a wettable, high strength foam material that has an ideal amount of stiffness and modulus (defined by Young's Modulus), depending on the application, without losing its strength properties.